Marker for use in a magnetic anti-theft security system and method for marking the marker

Abstract

A marker for use in a magnetic anti-theft security system has an amorphous ferromagnetic alloy alarm strip and at least one activation strip. The semi-hard magnetic alloy for the activation strip contains 8 to 25 weight % Ni, 1.5 to 4.5 weight % Al, 0.5 to 3 weight % Ti and balance of iron. The alloy is distinguished over known, employed alloys by excellent magnetic properties and a high resistance to corrosion. Further, the alloy can be excellently cold-worked before the annealing.

What is claimed is:  
     
       1. A method for manufacturing an activation strip for a magnetic anti-theft security system, comprising the steps of: 
       providing an alloy having a composition 8 to 25 wt % Ni, 1.5 to 4.5 wt % Al, 0.5 to 3 wt % Ti, and a remainder of iron;  
       melting said alloy in an environment selected from the group consisting of a vacuum and a protective atmosphere to obtain a melted alloy, and casting said melted alloy into an ingot;  
       hot working said ingot to form a ribbon at a temperature above approximately 800° C.;  
       annealing said ribbon at a temperature above approximately 800° C.;  
       rapidly cooling said ribbon to produce a cooled ribbon having a cross-section;  
       cold-working said cooled ribbon and thereby reducing the cross-section thereof by approximately 90%, to obtain a cold-worked ribbon;  
       annealing said cold-worked ribbon in a range between approximately 650° and 700° C. to obtain a cold-worked and annealed ribbon having a cross-section;  
       cold-working said cold-worked and intermediately annealed ribbon to reduce the cross-section thereof by at least 60% to obtain a twice cold-worked ribbon;  
       annealing said twice cold-worked ribbon at a temperature in a range between approximately 400° and 600° to obtain a finished ribbon; and  
       cutting and trimming said finished ribbon into a plurality of activation strips, said activation strips having a coercive force H c  between and 10 and 24 A/cm and a remanence B r  of at least 1.3 T.  
     
     
       2. A marker for magnetic anti-theft security system, comprising: 
       an oblong alarm strip of an amorphous ferromagnetic alloy;  
       at least one activation strip of a semi-hard magnetic alloy;  
       said semi-hard magnetic alloy comprising:  
       8 to 25 wt % Ni,  
       1.5 to 4.5 wt % Al,  
       0.5 to 3 wt % Ti;  
       a remainder of iron; and  
       said semi-hard magnetic alloy having a coercive force H c  between 10 and 24 A/cm and a remanence B r  of at least 1.3 T.  
     
     
       3. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one constituent selected from less than 5 wt % Co, and less than 3 wt % Mo or Cr. 
     
     
       4. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one element selected from the group consisting of Zr, Hf, Nb, Ta, Mn and Si, wherein each selected element is less than 0.5 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy. 
     
     
       5. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one element selected from the group of elements consisting of C, N, S, P, B, H, and O, wherein each selected element is less than 0.2 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy. 
     
     
       6. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one constituent selected from less than 5 wt % of Co, and less than 3 wt % Mo or Cr, and 
       at least one element selected from the group consisting of Zr, Hf, Ta, Nb, Mn and Si, wherein each selected element is less than 0.5 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy.  
     
     
       7. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one constituent selected from less than 5 wt % of Co, and less than 3 wt % Mo or Cr, and 
       at least one element selected from the group consisting of C, N, S, P, B, H, and O, wherein each selected element is less than 0.2 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy.  
     
     
       8. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one constituent selected from the group consisting of Zr, Hf, Ta, Nb, Mn and Si, wherein each selected element is less than 0.5 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy; and 
       at least one element selected from the group consisting of C, N, S, P, B, H, and O, wherein each selected element is less than 0.2 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy.  
     
     
       9. A marker as claimed in  claim 2  wherein said semi-hard magnetic alloy further comprises at least one constituent selected from less than 5 wt % of Co, and less than 3 wt % Mo or Cr; 
       at least one element selected from the group consisting of Zr, Hf, Ta, Nb, Mn and Si, wherein each selected element is less than 0.5 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy; and  
       at least one element selected from the group consisting of C, N, S, P, B, H, and O, wherein each selected element is less than 0.2 wt % of the alloy and all selected elements in total are less than 1 wt % of the alloy.